The 6 cell packs have a 22.2v nominal charge. 2 would work for a 48v.

Each Cell is 3.6v Nominal with 4.2v fully charged. Think like regular ole alkaline batteries where an AA is 1.5v :)

I have no affiliation with Hobby King they are just a cheap place to get battery packs motors speed controllers and other tinkering gear.
https://hobbyking.com/en_us/batteries/lipo-batteries-all-brands.html